editorial advice please

the equivalent amount in euros

presumably after correction for inflation. Inflation from 1880 to today in Britain is about 50 times, which makes that 12/- wage worth only £30 today, a reminder of how poor people were in those days compared to today.

There are two inflation comparison methods:
http://www.measuringworth.com/ppoweruk/
According to that site, 12 shillings in 1880 was in 2012 terms (the latest year they give) £50.60 using the retail price index, £263.00 using average earnings.

There are not many farm labourers around these days, but I see the average weekly wage for a typist is £18,486 a year, according to this site:
http://www.reed.co.uk/average-salary/admin-secretarial-pa/typist
Divided by 52, that works out to £355.50 a week.

The amount in euros is given to provide an order of magnitude of expenses, but any mentions of salaries, for example, are comparisons with workers or farm labourers at the time.

Of course it's meaningless to give an exact equivalence because of inflation as well as the change in French currency in 1960 -- 100 francs became 1 new franc,

Another North American here, voting with the posters above who recommend the use of metric. It makes no sense to me to use measurements that will be easily understood by only a tiny percentage of your book's readers. Let them read what's between the parentheses.

If the book is mainly to be sold in France to tourists, it would be weird to use American English, no?

I'm agreeing with all the posters, too. Your work is European. There is no shame in using british spellings and metric measures.

Personally, as an engineer who has worked in the US and in Europe, I see the imperial measurement system as a mind-rotting plague, based on an historical mistake that has turned out to be too difficult to correct in the US for a lot of reasons (eg, "it's a communist plot") that aren't worth delving into here. We shouldn't encourage its continued use (except maybe in golf, where 2-foot putts sound better than 60-centimeter putts).

If the book is mainly to be sold in France to tourists, it would be weird to use American English, no?

Is it known that every place in France gets more British tourists than USAnian?

Is it known that every place in France gets more British tourists than USAnian?

Seems like a pretty safe bet (a known unknown as someone famously said). Possible exception: the US Embassy in Paris.

Is it known that every place in France gets more British tourists than USAnian?

I'd hazard a guess that France gets more people who speak British English than American English, even if they aren't British. That is, most of those "other English-speaking Europeans" were probably taught British English.

Well, nutrax in school we're taught british english, but where I live we had a lot of american soldiers and before 9/11 they were out in our economy much more than british speaking people, my ex even had to translate british english into american english in London for me, so my friends and I are more likely to use american english.

Sorry, for the OT bjd, use british english in your translation.